In recent years, non-aqueous electrolyte secondary batteries having a high energy density have been widely used as drive power sources for high output applications, such as an electric power tool, an electric assist bicycle, and a hybrid electric automobile. The non-aqueous electrolyte secondary battery is roughly classified based on its outer shape or outer package, into a cylindrical battery, a square battery, and a pouch type battery. Since having a strong resistance against impact from the outside and being easily assembled into a battery pack using many batteries, the cylindrical battery is preferably used for the above application.
The cylindrical battery is formed in such a way that after an electrode body formed by winding a negative electrode plate and a positive electrode plate with at least one separator interposed therebetween is inserted into an outer can, an open portion thereof is sealed by a sealing body. In a general cylindrical battery, since the sealing body functions as a positive electrode external terminal, the positive electrode plate and the sealing body are required to be electrically connected to each other. Hence, as a method for this purpose, a method in which a lead connected to the positive electrode plate is connected to the sealing body has been mainly used in the non-aqueous electrolyte secondary battery.
However, according to the method described above, a current collector portion of the positive electrode plate is limited to a connection portion of the positive electrode lead. Hence, even if the length of the positive electrode plate is increased, sufficient output characteristics may not be obtained in some cases. Accordingly, a plurality of leads is connected to the positive electrode plate so as to optimize the current collector structure of the non-aqueous electrolyte secondary battery. As related art documents on a battery having a positive electrode plate to which a plurality of leads is connected, Patent Documents 1 to 3 may be mentioned.
Patent Document 1 has disclosed a secondary battery in which leads extending from an electrode body are overlapped with each other at one point, and this overlapped portion is connected to a sealing body.
Patent Document 2 has disclosed an electrode winding type battery in which a plurality of leads extending from an electrode body is electrically connected to a conductive member disposed on the electrode body. The conductive member is formed of a nut and a bolt having a flange portion, and the leads extending from the electrode body are each bent onto the flange portion of the bolt and are fixed between the bolt and the nut.
Patent Document 3 has disclosed a nickel cadmium battery in which a plurality of electrode plate tabs extending from a spiral electrode group is connected to an intermediate plate functioning as a current collector plate. Between the electrode group and the intermediate plate, an insulating plate is disposed, and many arc-shaped openings into which the electrode plate tabs are to be inserted are provided in the intermediate plate and the insulating plate. The electrode plate tabs inserted into the arc-shaped openings are bent on the intermediate plate and are connected thereto.